How do I show the video preview?
I figured it out thanks to this question:

First, you want to look for the 'window selector' icon, and click it, and choose the 'Video Sequence Editor' option:



Next, if you don't immediately see the video preview, you want to click a button on the bottom of that window that has a red-and-white checkerboard pattern, that will switch the window to be a video preview:



Finally, if the zoom is somehow messed up so that you don't see the entire image in the window, click the 'View' dropdown and choose the 'Fit preview in window' option:



And when all that's done, this is what the window should look like: